Figure 1. Disposable plastic cartridge for handling liquids.
Methods The simplicity of the cartridge is an important point at the manufacturing stage and during use of the cartridge. It is important that the cartridge contains as few components as possible. Fewer separate components mean fewer moulds and mouldings and simpler final assembly. The cartridge should also be easy to use and, if necessary, the functions should be operated without external devices. Commercial thermoplastics are an economical choice of raw material for the cartridge. In the Ruiskuchip project, polycarbonate (PC), polystyrene (PS), polypropylene (PP) and cyclic polyolefin (COC) were observed to be the most suitable materials due their processability and optimal mechanical, chemical and optical properties. The functionality of the cartridges was based on the surface and gravity forces and simple ways to generate under- and over-pressure. The sampling and dosing were solved by special accurate containers and the use of innovative multi-use valves that can be manufactured by injection moulding. Several types of pumping components were developed and
manufactured. They can all be made by injection moulding and easily integrated into a disposable plastic cartridge. The sealing of the cartridge is also an essential manufacturing stage. It usually means bonding the cover to the cartridge. The thermal processes and use of adhesives easily destroy the reagents and analytes if they are integrated into the cartridge before sealing. The micro-features inside the product place special demands on the bonding process. In the project, an effective laser welding process was developed for the sealing step. The process made accurate positioning of the bonding area possible without destroying of the micro-features and analytes inside the cartridge. It is also suitable for low-cost mass manufacturing of the products.
Results In the project, several demonstration cartridges were developed and manufactured for sampling, dosing, transferring and mixing the liquids.
Production matters. VTT in global trends. Kai Häkkinen (ed.)